I don't know Agilent's current stance on this but I can say that I recently used a 3rd-party library which was compiled for .NET 4.0 ( with 9.31 or 9.32 ) and I simply could not pursuade it to work properly. I can't remember the problem but I think it initialised okay but ignored any commands. As the library was open-source I recompiled it for .NET 3.5 which works fine. I have seen threads on a similar theme and AFAIR there were no success stories with 4.0 libraries.

I'm sure that later versions will be on the roadmap but Agilent are giong to be internally focussed for the next year or so as they are cast off into their new company Keysight; I wouldn't expect VEE X ( mentioned over 2 years ago ) is unlikely to emerge any time soon in my estimation.

Have a look in the VRF, there was a "cheat" supplied to use dotnet4 with VEE 9.32 - but still keep in mind that not officially supported yet. the cheat consists of some editing of the vee,config file..